Unit Name: Reston Formation
Unit Type: Lithostratigraphic
Rank: Formation
Status: Formal
Usage: Currently in use
Age Interval: Bajocian ? (171.6 - 167.7 ma)
Province/Territory: Manitoba

Originator: Stott, 1955.

Type Locality:
Named for subsurface occurrence in southwestern Manitoba, but no type section defined. Outcrop now known to occur on Turtle River (SW/4 Twp. 24, Rge. 15WPM), south of St. Rose du Lac. Suggested subsurface reference section is in the well Tudale Neepawa 5-29-24-14WPM, between 197.8 and 214.7 m (649 and 704 ft) completely cored.

The Reston ranges from zero to 45.7 m (150 ft) in thickness in southwestern Manitoba, to as much as 61 m (200 ft) for equivalent strata in the central part of the Willison Basin. The formation thins to the north, and north of Virden (approx. Twp. 12), near the Saskatchewan border overlaps a Paleozoic paleotopographic high, pinching out north of about Twp. 15. East of the paleotopographic high the Reston extends as far north as Twp. 28. The name is applied only in southwestern Manitoba, where it is also referred to informally as the "Jurassic Lime".

Locality Data:
Thickness(m): Minimum 0, Maximum 61.

Interbedded light buff, dolomitic, argillaceous and partly sandy limestones, and dark grey to greenish grey, rarely reddish to yellowish brown shale. Limestone interbeds are thicker and more common towards top of unit which is marked by a persistent sandy and oolitic bed. Anhydrite and gypsum are present locally.

The unit conformably overlies evaporites of the Amaranth (Watrous) Formation, except north of Virden, where it rests unconformably on Mississippian limestones of the Lodgepole Formation. It is overlain with slight unconformity by variegated shales and sands of the Melita Formation. It correlates with the lower Gravelbourg of Saskatchewan and with part of the Piper of North Dakota.

Other Citations:
Bannatyne, 1975; Stott, 1955.

Bannatyne, B.B., 1975. High-calcium limestone deposits of Manitoba; Man. Dept. Mines Res. and Env. Management, Pub. 75-1.
Stott, D.F., 1955. Jurassic stratigraphy of Manitoba; Manitoba Dept. Mines and Nat. Res., Pub. 54-2.

Source: CSPG Lexicon of Canadian Stratigraphy, Volume 4, western Canada, including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba; D.J. Glass (editor)
Contributor: H .R. McCabe
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 22 Mar 2011